Various psychiatric disorders are treated with mindfulness-based interventions (MBIs), although the efficacy of MBIs in patients with social anxiety disorder (SAD) is unclear. In this meta-analysis, we investigated the efficacy of MBIs on SAD symptoms. Systematic searches were performed in various databases, and 11 eligible randomized controlled trials (RCTs) and 5 single-arm trials were identified. The between-groups analysis of the 11 RCTs showed that Hedges’ g = 0.00, while the within-group analysis showed a large pre-post effect size (g = 1.20). MBIs were superior to the no-treatment comparator (g = 0.89), equivalent to specific active treatment (g = –0.19), and less effective than evidence-based treatment (i.e., cognitive behavioral therapies) (g = –0.29).MBIs significantly alleviated depressive symptoms and improved mindfulness, quality of life, and self-compassion. Meta-regression analysis showed a dose–response relationship between the alleviation of SAD symptoms and the duration of the MBIs (β = 0.659). Follow-up analysis showed that the effects of MBIs on SAD persisted for 12 months (g = 0.231). An analysis of the 5 single-arm trials found that MBIs had a medium effect in alleviating SAD symptoms (g = 0.48). Future research is needed regarding the design of large RCTs of MBIs on SAD patients.